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Kernel: Add character device driver for the RPi "mini UART" (UART1)

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While the PL011-based UART0 is currently reserved for the kernel
console, UART1 is free to be exposed to the userspace as `/dev/ttyS0`.
This will be used as the stdout of `run-tests-and-shutdown.sh` when
testing the AArch64 kernel.
This commit is contained in:
Daniel Bertalan 2023-05-15 07:51:46 +02:00 • committed by Andrew Kaster
parent 3beb488887
commit c460b84ebe
4 changed files with 186 additions and 0 deletions
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47
Kernel/Arch/aarch64/RPi/MiniUART.h Normal file
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/*
* Copyright (c) 2023, Daniel Bertalan <dani@danielbertalan.dev>
*
* SPDX-License-Identifier: BSD-2-Clause
*/
#pragma once
#include <Kernel/Devices/CharacterDevice.h>
#include <Kernel/Devices/DeviceManagement.h>
#include <Kernel/Locking/Spinlock.h>
namespace Kernel::RPi {
struct MiniUARTRegisters;
// Makes the secondary "mini UART" (UART1) available to the userspace.
// See bcm2711-peripherals.pdf chapter "2.2. Mini UART".
class MiniUART final : public CharacterDevice {
friend class Kernel::DeviceManagement;
public:
static ErrorOr<NonnullLockRefPtr<MiniUART>> create();
virtual ~MiniUART() override;
// ^CharacterDevice
virtual bool can_read(OpenFileDescription const&, u64) const override;
virtual ErrorOr<size_t> read(OpenFileDescription&, u64, UserOrKernelBuffer&, size_t) override;
virtual bool can_write(OpenFileDescription const&, u64) const override;
virtual ErrorOr<size_t> write(OpenFileDescription&, u64, UserOrKernelBuffer const&, size_t) override;
void put_char(u8);
private:
MiniUART();
// ^CharacterDevice
virtual StringView class_name() const override { return "MiniUART"sv; }
void set_baud_rate(u32);
bool m_last_put_char_was_carriage_return { false };
Spinlock<LockRank::None> m_serial_lock {};
MiniUARTRegisters volatile* m_registers;
};
}